From the Guidelines
To treat urinary retention caused by diphenhydramine (Benadryl), discontinue the medication immediately and consider intermittent catheterization for initial management, as recommended by the American Heart Association/American Stroke Association 1. For mild cases, time and hydration may resolve symptoms within 24-48 hours as the medication clears from your system. In more severe cases, a healthcare provider may prescribe bethanechol (Urecholine) at 10-50 mg orally three to four times daily to help stimulate bladder contraction. For acute severe retention, catheterization may be necessary to relieve pressure and drain the bladder. Tamsulosin (Flomax) 0.4 mg daily may also be prescribed to relax the urethral sphincter and improve outflow, although its use should be considered with caution in patients with certain medical comorbidities, as noted in the AUA guideline on management of benign prostatic hyperplasia 1. Diphenhydramine causes urinary retention through its anticholinergic properties, which block acetylcholine receptors that normally stimulate bladder muscle contraction. Elderly patients and those with prostatic hypertrophy are at higher risk for this side effect. To prevent recurrence, avoid other anticholinergic medications and consider non-sedating antihistamines like cetirizine or loratadine as alternatives for allergy symptoms. Some key points to consider when treating urinary retention caused by diphenhydramine include:
- Discontinuing the medication immediately to prevent further anticholinergic effects
- Screening for urinary retention via bladder scan or straight catheterization, as recommended by the American Heart Association/American Stroke Association 1
- Considering intermittent catheterization for initial management, as recommended by the American Heart Association/American Stroke Association 1
- Prescribing bethanechol (Urecholine) or tamsulosin (Flomax) to help stimulate bladder contraction or relax the urethral sphincter, respectively.
From the Research
Treatment of Urinary Retention Caused by Diphenhydramine
- The provided studies do not directly address the treatment of urinary retention caused by diphenhydramine (Benadryl) 2, 3, 4, 5, 6.
- However, some studies discuss the treatment of acute urinary retention (AUR) in general, which may be relevant to urinary retention caused by diphenhydramine.
- According to a study published in 2007, the immediate treatment for AUR is bladder decompression using urethral or suprapubic catheterization 2.
- Another study published in 2006 discusses the use of alpha blockers, such as tamsulosin, to prevent AUR in symptomatic BPH patients and facilitate catheter removal following episodes of spontaneous AUR 3.
- A study published in 2005 found that tamsulosin can help men with AUR caused by BPH to void more successfully after catheter removal and reduce the likelihood of needing re-catheterization 4.
- A 2006 study recommends the use of alpha-adrenergic antagonists, 5-alpha-reductase inhibitors, and a trial without catheter to delay or prevent the need for surgery and future complications in patients with AUR 5.
- It is essential to note that diphenhydramine is an antihistamine with many side effects, including sedation and risk of toxicity in overdose, and its use should be carefully considered, especially when alternative medications are available 6.
Possible Treatment Approaches
- Bladder decompression using urethral or suprapubic catheterization may be necessary to relieve urinary retention caused by diphenhydramine 2.
- Alpha blockers, such as tamsulosin, may be used to help manage urinary retention caused by diphenhydramine, although this is not directly supported by the provided studies 3, 4.
- Discontinuing the use of diphenhydramine and considering alternative medications may also be necessary to prevent further urinary retention episodes 6.